Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$33.78	12.564%	$38.0241	$38.02	$38.00	$38.00
Purchase #2	$95.83	10.585%	$105.9736	$105.97	$105.95	$106.00
Purchase #3	$62.53	5.314%	$65.8528	$65.85	$65.85	$65.90
Purchase #4	$65.91	6.289%	$70.0551	$70.06	$70.05	$70.10
Purchase #5	$213.71	6.238%	$227.0412	$227.04	$227.05	$227.00
Purchase #6	$199.37	10.260%	$219.8254	$219.83	$219.85	$219.80
Purchase #7	$55.52	8.344%	$60.1526	$60.15	$60.15	$60.20
7 purchase totals =	$726.65		$786.9248	$786.92	$786.90	$787.00